1. Field of the Present Invention
The present invention generally relates to the field of power management in an electronic system and more particularly to the circuit and method for controlling line drivers in a system with multiple power modes.
2. History of Related Art
Electronic systems including computer systems are frequently designed with a multiple power supply scheme to permit multiple power mode operation. Multiple power modes enable the system to assume one of two or more power states depending upon various factors. In one example familiar to many users of computer systems, portions of the computer system including disk drives, display screens, and possibly an attached printer will be effectively turned off if the devices has not detected any recent activity. Low power modes beneficially reduce power consumption and preserve or extend the useful life of system components by decreasing the amount of thermal stress to which the components are subjected. Semiconductor components, for example, are susceptible to failure or breakdown from sustained thermal stress. Moreover, there is a direct relationship between the power consumed by a semiconductor device and the temperature of the device. For these reasons, it is highly desirable to design the system that consumes the lowest possible power consumption in its low power mode. Unfortunately, it is not uncommon to have a low power mode portion of a system connected to another portion of the system that is not operating in low power mode. This arrangement can lead to undesirable results in the form of increased low power mode current and possibly even damaged components when an output driver or line driver of the preceding stage remains powered while power is terminated to the driven stage. Accordingly, it would be highly desirable to implement an elegant yet practical solution to managing line drivers in a power managed system.